Electro-acoustic submarine transducer



Oct. 24, 1967 M. M. HANFF 3,34

ELECTRO-ACOUSTIC SUBMARINE TRANSDUCER Filed Nov. 30, 1965 Pia].

United States Patent w 3,349,366 "ELECTRO-ACOUSTIC SUBMARINE TRANSDUCERMichel Max Hanlf, Brest, France, assignor to Compagnie des Compteurs,Paris, France, a company of France Filed Nov. 30, 1965, Ser. No. 510,513Claims priority, application France, Dec. 3, 1964,

997,222, Patent 1,425,383

9 Claims. (Ci. 340-8) The present invention relates to electro-acousticsubmarine transducers intended to be immersed in the sea fortransmitting sound waves. with especially very low frequencies rangingfrom a few cycles per second.

In numerous submarine applications, such as communication, detection,prospection, acoustical dredging, etc. there is necessary to realizerather powerful transmission of sound waves under sea.

The known devices for electro-acoustical conversion generally are notsuitable to operate under water as they have various disadvantages.Owing to the energy required for starting up vibrations in the diaphragmof the transducer located in the liquid medium, very large currents arealso required. Windings thus are difiicult to cool. Moreover at lowfrequencies such devices transmit like pulsating spheres, with nodirective power contrarily to what is required in some applications. Inthe last place they are designed to be heavy and expensive.

The invention relates to an electro-acoustical transducer by which suchdisadvantages are substantially reduced.

The transducer according to the invention being of theelectro-dynarnical type, including a free-flooding magnetic yoke with acentral core having an annular airgap in which a radial magnetic fielddrives an axially movable coil disposed on a horn, is particularlycharacterized by the following features:

(a) The yoke is drilled with holes providing circulation of the water inwhich the transducer is immersed so as to allow direct and efficientcooling of coils.

(b) The coil is placed around a cylindrical part of the horn whichslides with along the core by an easy fitting.

(c) The horn also includes a suitable plate, generally perpendicular tothe axis of the transducer, connected to the yoke by adjustableresilient guiding means.

A magnetic field in the airgap may be produced by a permanent magnetlocated, for instances, in place in the core, or by a winding carryingdirect current, surrounding the core, also cooled by direct contact withwater.

Other characteristics of the invention will be revealed by the followingdescription together with the attached drawings showing, by way ofnon-restrictive examples, two forms of embodiment of the transduceraccording to the invention as seen by means of axial sectional views.

FIG, 1 is a cross-sectional elevation of one embodiment of thetransducer according to the invention.

FIG. 2 is a diagram of a ship carrying the transducer of FIG. 1.

FIG. 3 is a cross-section elevation similar to FIG. 1, showing anotherform of embodiment.

In FIG. 1, 1 designates the magnetic yoke being in the form of acylindrical pot and 2 the central cylindrical core which together withan annular magnetic plate 10, fitted on the yoke, establishes an annularairgap 3 therebetween. The magnetic yoke 1 is free-flooding in the sensethat it lies in direct contact with the water in which it is immersed.

4 designates a movable coil, mounted on a tubular sheath made integrallywith the horn 5, which is made of two parts 5a, 5b, for instance, from alight metal secured to each other by any suitable fixing means. Part 5awith a cylindrical shape is made at its lower end into a wide flange 6in which coil 4 is mounted; part 5b is a flat circular plate in thecenter of which there is provided a circular hole 7 having a diameter ofessentially the same size as that of core 2.

Coil 4 is fed with current by way of leads 4a which are supported inhermetically sealed insulating plugs 21 and 21a respectively fitted inpart 5a and the core 2 into which leads 4a are advantageously passed.

The assembly of movable elements 4-5 is yieldingly connected to yoke 1by means of, for instance, four upper compression springs 8, and fourlower compression springs 8. The upper and lowerrhelical springs 8, 8'are in axial alignment and are spaced uniformly apart, i.e. at aroundthe cylindrical yoke 1. The springs are carried on rods 9 having lowerthreaded end portions which are screwed into threaded holes in theannular plate 10, and the upper ends of the rods 9 are likewise threadedand receive a stabilizing ring 19 to maintain the rods 9 parallel toeach other. Nuts 13 screwed onto the upper ends of the rods 9 againstring 19 serve to hold the ring in place and also to adjust the springs8, 8'. The annular plate part 512 of the horn is provided with fourapertures 11 to enable this part to be supported on rods 9 between theupper and lower sets of springs 8, 8, so as to guide the movableassembly 45. Further guiding around core 2 is ensured in providing aneasy fitting between the lower portion 6 of part 5a and a sheath 12applied to the periphery of core 2 and which is made of some materiallike superpolyamid that is, for example, known under the name of nylonor Rilsan. Compression springs 8, 8 when adjusted by means of nuts 13serve to set coil 4 in a suitably high position within airgap 3.Flexible stops 14 limit movement of the transducer horn element 5.

Holes 15 are provided in yoke 1 so that when coil 4 is supplied with analternating current thus causing assembly 4-5 to reciprocate it induceswater to be circulated around coils 4 and 17 which thus providesefiicient cooling thereof. Further holes such as 16, are provided aslateral passages for leads 17a feeding excitation coils 17. Coils 17located within an annular recess 1 in the yoke 1 and communicating withthe annular gap 3 are fed with direct current so that a continuousbiasing magnetic field is produced in airgap 3. Coil 4 on the contraryis fed with alternating current for the production of an alternatingfield causing horn 5 and coil 4 thereon to be reciprocated in an axialdirection at a frequency which is the same as that of said alternatingcurrent. A hoist ring 20 is screwed into the periphery of the yoke 1 inorder to enable the transducer to be raised and lowered.

A stabilizer 18 consisting for instance of a wood plate with largediameter is advantageously attached to the transducer the plate 18 beingheld against and fixed to the bottom of yoke 1 by any suitable means.When coils 4 and 17 are energized the reciprocating fiat plate 51) ofthe horn stirs up water, but contrarily to what occurs in known devices,does not compress it. It thus functions as a transducer which behaveslike an acoustic dipole allowing transmission of sound waves producedtherefrom to be directed to some extent. Due to its structure theimproved transducer does not require pressure compensation; on thisaccount, it can be immersed at considerably variable depths.

The frequency range of this type of transducer starts from below 5 Hz.,whereas the resonant frequency thereof is at about Hz., without beinghighly expressive. Since, owing to these frequencies being very low,baffies should be of very considerable dimensions (several tens ofmetres), there is provision for the transducer according to theinvention to be mounted on the ships hull the latter thus beingsubstituted for a baffle. This can be seen in FIG. 2 where a recess 22is provided in ships hull for the transducer to be partly attachedthereto.

FIG. 3 shows a further embodiment of the invention wherein theelectrically energized biasing coils 17 of FIG. 1 are replaced by apermanent magnet 23 which is shown as being a radially biasing magnetinserted in the cylindrical core 2 and being of the same diameter as thecore. Operation of such as modified transducer is obviously similar tothat of FIG. 1.

What I claim is:

1. In an electr c-acoustic transducer structure for sub marine use inthe transmission of sound Waves through the water, the combinationcomprising a free-flooding annular yoke member of magnetic material indirect contact with the water when said transducer structure is immersedtherein, a core of magnetic material located concentrically within saidannular yoke member and spaced radially therefrom to establish anannular gap therebetween, means for producing a continuous biasing fieldin a magnetic circuit through said yoke and core, a horn comprising aplate-like member and a downwardly extending tubular portion projectinginto said annular gap, resilient means carried by said yoke member andsupporting said horn for permitting a reciprocating motion thereof, adriver coil applied to said tubular portion of said horn within said gapand adapted to be energized with alternating current thereby to effectreciprocation of said horn, and cooling means comprising a passagewayextending through said yoke from the exterior thereof to said annulargap to provide for free circulation of the Water in which saidtransducer structure is immersed into said annular gap thereby to removeheat from said driver coil.

2. A submarine electro-acoustic transducer structure as defined in claim1 and Which further includes a thin sheath of material such as asuperpolyamid applied to the periphery of said core to establish an easysliding fit with said tubular portion of said horn.

3. A submarine electr c-acoustic transducer structure as defined inclaim 1 wherein said plate-like member of said horn is supported by saidresilient means and includes a central opening therein of a diametercorresponding to that of said tubular portion and communicating with theinterior thereof to facilitate reciprocation of said horn.

4. A submarine electro-acoustic structure as defined in claim 1 whereinsaid resilent means supporting said horn for reciprocatory movement iscomprised of a plurality of circumferentially spaced rods secured at oneend thereof to said yoke and extending axially of the yoke, saidplate-like member of said horn being provided with spaced apertures toestablish pass-through points for said 4 rods, a first set ofcompression springs located on said rods between said yoke and one sideof said plate-like member, a second set of springs located on said rodsbetween the opposite side of said plate-like member and the oppositeends of said rods, a centering ring for said rods having aperturestherein establishing pass-through points for said opposite ends of saidrods to engage the corresponding ends of; said springs of said secondset, and means for applying an adjustable pressure to said centeringring and thence to said springs to eifect a corresponding adjustment inthe position of said horn member relative to said yoke and core.

5. A submarine electro-acoustic transducer structure as defined in claim4 and which further includes flexible stop means surroundingrespectively the springs of said first set and which serve to limitmovement of said platelike member of said horn in the direction of saidyoke.

6. A submarine electro-acousti transducer structure as defined in claim1 and which further includes a flat mounting plate of non-magneticmaterial of larger area than said yoke, said mounting plate beingsecured to said yoke at the side opposite said annular gap and includingpassageways therethrough in alignment with said passageway meansextending through said yoke and which provide for circulation of waterinto said annular gap.

7. A submarine electro-acoustic transducer structure as defined in claim1 wherein said yoke is provided with an annular recess and wherein saidmeans for producing said continuous biasing field is constituted by coilmeans located in said annular recess and adapted to be energized withdirect current, said annular recess being in communication with saidannular gap thereby to also establish therein a circulation of Water-for cooling said coil means.

8. A submarine electro-acoustic transducer structure as defined in claim1 wherein said means for producing said continuous biasing field isconstituted by a permanent magnet inserted in said core.

9. A submarine electro-acoustic transducer structure as defined in claim1 and which further includes bafiie means constituted by the hull of aship to which said transducer structure is secured.

References Cited UNITED STATES PATENTS 1,808,149 6/1931 Smith.

2,432,218 12/1947 Vang.

2,510,315 6/1950 Granche.

2,977,573 3/1961 Mott 340-44 RODNEY D. BENNETT, Primary Examiner.CHESTER L. JUSTUS, Examiner. R. L. RIBANDO, Assistant Examiner.

1. IN AN ELECTRO-ACOUSTIC TRANSDUCER STRUCTURE FOR SUBMARINE USE IN THETRANSMISSION OF SOUND WAVES THROUGH THE WATER, THE COMBINATIONCOMPRISING A FREE-FLOODING ANNULAR YOKE MEMBER OF MAGNETIC MATERIAL INDIRECT CONTACT WITH THE WATER WHEN SAID TRANSDUCER STRUCTURE IS IMMERSEDTHEREIN, A CORE MAGNETIC MATERIAL LOCATED CONCENTRICALLY WITHIN SAIDANNULAR YOKE MEMBER AND SPACED RADIALLY THEREFROM TO ESTABLISH ANANNULAR GAP THEREBETWEEN, MEANS FOR PRODUCING A CONTINUOUS BIASING FIELDIN A MAGNETIC CIRCUIT THROUGH SAID YOKE AND CORE, A HORN COMPRISING APLATE-LIKE MEMBER AND A DOWNWARDLY EXTENDING TUBULAR PORTION PROJECTIONINTO SAID ANNUALR GAP, RESILIENT MEANS CARRIED BY SAID YOKE MEMBER ANDSUPPORTING SAID HORN FOR PERMITTING A RECIPROCATING MOTION THEREOF ADRIVER COIL APPLIED TO SAID TUBULAR PORTION OF SAID HORN WITHIN SAID GAPAND ADAPTED TO BE ENERGIZED WITH ALTERNATING CURRENT THEREBY TO EFFECTRECIPROCATION OF SAID